1. Field of the Invention
The present invention relates to a process of producing an IC card with an IC module embedded therein and more particularly to such an IC card which comprises a single core sheet, cover films formed over the core sheet on the opposite sides to form a substrate with the core sheet and an IC module embedded in a cavity that is formed in the substrate.
2. Description of the Prior Art
In recent years, various types of cards such as cashing cards, credit cards, membership cards, hospital consultation cards and other cards have broadly been used and are being essential in our daily life. At the present time, such cards are mainly in the form of a magnetic card. However, the magnetic card has its limit in functional extension since the memory capacity is too small and also problems in security and reliability. In order to overcome such problems, a multi-function IC card has been proposed which has an increased memory capacity and an improved security function and which includes CPU, memory chip and the like.
The IC card may be produced by any one of various methods. West Germany Patent No. 30299399 discloses a process of producing an IC card which has an IC module and its external connection terminals mounted and enclosed in a support to protect the IC module from a mechanical stress. The support, IC module and external connection terminals are assembled into an integral unit which is inserted in a cavity formed in the inner layer of the card before the integral unit is sealed by hot lamination. However, such a process requires any special measure for preventing the sensitive IC module from being damaged by pressure and/or temperature during the hot lamination, such as a buffer zone formed in the laminated card.
Another process has been proposed which after the card body has been laminated, it is machined by the end mill to form a blind hole into which the IC module can be fitted. This process is very difficult to provide a high-quality card since much dusts and shavings are produced and attracted by electrostatic charges inherent in the synthetic films and raises a further problem in that the IC card is produced through the increased number of working steps with degradation of the accuracy of finishing.
A further process of making an IC card with IC module has been proposed which can eliminate the shortcomings in the hot lamination process while maintaining its advantages, as in Japanese Patent Publication No. Sho 63-42314. As shown in FIGS. 1A to 1D in the accompany drawings, a multi-layer card comprises a hot laminated card body 40 including cover films 41, 42 and an intermediate layer 43 therebetween. A separation layer 45a or 45b, as formed from a mixture of solvent and silicon, is sandwiched between each of the cover films 41 or 42 and the intermediate layer 43 at a position in which an IC module 44 is to be located. Two different punch dies 47a and 47b are used to form two recesses connecting with each other and having different diameters corresponding to the respective separation layers 45a, 45b to provide a cavity receiving the IC module by punching the card body 40 until one of the punch dies 47b reaches the inner face of the lower cover film 42. The punched material portions 48a, 48b are removed with the cut separation layers 45a, 45b. Finally, the IC module 44 is fitted into the recesses 46a, 46b so formed.
Prior to filing of Japanese Patent Publication No. Sho 63-42314, Japanese Patent Publication No. Sho 52-2640 discloses a technique of forming separation layers at a cavity to receive the IC module. More particularly, such a technique forms a cavity to receive a cipher panel in a composite ID card which comprises a white-colored plastic sheet having the opposite printed sides and a separatable layer partially formed in the sheet on one side and adapted to be formed with a cipher area, and transparent plastic sheets heat-sealed to the white-colored plastic sheet on the opposite sides, by cutting the composite card along the outline of the cipher area and separating a portion of the transparent plastic sheet corresponding to the cipher area from the white-colored plastic sheet.
The prior art as disclosed in Japanese Patent Publication No. Sho 63-42314 has the following problems. As seen from FIGS. 1A to 1D, shavings of the card materials and separation layers remain in the IC module receiving cavity (46a, 46b) after it has been punched out by the punching dies 47a and 47b accurately matching the recesses 46a and 46b in cross-section and depth. This requires an additional cleaning step for removing the shavings not to provide an obstruction to the subsequent steps such as adhering step and others.
When the card body is punched out by the punching dies, one of the punching dies 47b forms a nick 49 in the outer face of the lower cover film 42. Such a nick 49 degrades the appearance of the IC card. This is more remarkable if the outer face of the cover film 42 is glossy. After the card body has been punched out by the punching dies, an outwardly convex part may be formed in the outer face of the lower cover film 42. This is an obstacle to the subsequent step, for example, to a step of adhering the IC module 44 to the card body 40. The nick 49 and convex part formed in the cover film 42 are also obstacles to the subsequent printing step. It is a matter of course that the formation of the nick and convex part is also provided by any pressing force sufficient to deform a thin cover film.